L. Varga

Isolation of Bacillus strains from the rhizosphere of cereals and in vitro screening for antagonism against phytopathogenic, food‐borne pathogenic and spoilage micro‐organisms

Bacillus strains were isolated from the rhizosphere of cereals in order to be used as natural biocontrol agents (BCAs). They were screened for antagonism in vitro against various test micro‐organisms. The isolates showing antagonism were identified to species level. A combination of techniques was employed for the isolation of Bacillus species. Using the direct method, only one of the 25 isolates screened showed antagonistic properties. This strain (IFS‐01) was identified by means of API test strips and the ATB Plus computer programme. It proved to be Bacillus subtilis and consequently has been designated as Bacillus subtilis IFS‐01. This strain produced either a broad spectrum antimicrobial compound or several compounds with different activities. The fungi and Gram‐positive bacteria were more sensitive to the antagonistic isolate than the Gram‐negative bacteria. A Bacillus strain producing BCAs which can be used as biopesticides or organic preservatives has been isolated and identified.

Use of ozone in the dairy industry: A review

Ozone treatment is a cost-effective and eco-friendly food-processing technology. It has successfully been used for the removal of milk residues and biofilm-forming bacteria from stainless steel surfaces and in milk processing, including fluid milk, powdered milk products and cheese. Ozonation has been shown to prevent mould growth on cheese and inactivate airborne moulds in cheese ripening and storage facilities. Ozone treatment has also been found to be a promising method for reducing the concentrations of pollutants in dairy wastewaters.

Influence of chicory inulin on the survival of microbiota of a probiotic fermented milk during refrigerated storage

Inulin-supplemented and control probiotic fermented milks were produced using a dairy starter culture containingsStreptococcus thermophilus CHCC 742/2130,Lactobacillus acidophilus La-5 andBifidobacterium lactis Bb-12, and were then stored at 4°C for 6 weeks. Microbiological analyses were performed at weekly intervals. The results showed that the presence of inulin at 1 t o 5% (wt/v) did not influence significantly (P>0.05) the survival rates of eitherS. thermophilus orL. acidophilus. However, the addition of inulin at 5% (wt/v) had a significant beneficial effect (P<0.05) on the viability of bifidobacteria after 28 days of refrigerated storage.

Evaluation of culture media for selective enumeration of bifidobacteria and lactic acid bacteria

The purpose of this study was to test the suitability of Transgalactosylated oligosaccharides-mupirocin lithium salt (TOS-MUP) and MRS-clindamycin-ciprofloxacin (MRS-CC) agars, along with several other culture media, for selectively enumerating bifidobacteria and lactic acid bacteria (LAB) species commonly used to make fermented milks. Pure culture suspensions of a total of 13 dairy bacteria strains, belonging to eight species and five genera, were tested for growth capability under various incubation conditions. TOS-MUP agar was successfully used for the selective enumeration of both Bifidobacterium animalis subsp. lactis BB-12 and B. breve M-16 V. MRS-CC agar showed relatively good selectivity for Lactobacillus acidophilus, however, it also promoted the growth of Lb. casei strains. For this reason, MRS-CC agar can only be used as a selective medium for the enumeration of Lb. acidophilus if Lb. casei is not present in a product at levels similar to or exceeding those of Lb. acidophilus. Unlike bifidobacteria and coccus-shaped LAB, all the lactobacilli strains involved in this work were found to grow well in MRS pH 5.4 agar incubated under anaerobiosis at 37 °C for 72 h. Therefore, this method proved to be particularly suitable for the selective enumeration of Lactobacillus spp.

Short communication: Survival of the characteristic microbiota in probiotic fermented camel, cow, goat, and sheep milks during refrigerated storage

The objective of this study was to monitor the viability during storage of Lactobacillus acidophilus LA-5 (A), Bifidobacterium animalis ssp. lactis BB-12 (B), and Streptococcus thermophilus CHCC 742/2130 (T) in probiotic cultured dairy foods made from pasteurized camel, cow, goat, and sheep milks fermented by an ABT-type culture. The products manufactured were stored at 4°C for 42d. Microbiological analyses were performed at weekly intervals. Streptococcus thermophilus CHCC 742/2130 was the most numerous culture component in all 4 products both at the beginning and at the end of storage. The viable counts of streptococci showed no significant decline in fermented camel milk throughout the entire storage period. The initial numbers of Lb. acidophilus LA-5 were over 2 orders of magnitude lower than those of Strep. thermophilus CHCC 742/2130. With the progress of time, a slow and constant decrease was observed in lactobacilli counts; however, the final viability percentages of this organism did not differ significantly in the probiotic fermented milks tested. The cultured dairy foods made from cow, sheep, and goat milks had comparable B. animalis ssp. lactis BB-12 counts on d 0, exceeding by approximately 0.5 log10 cycle those in the camel milk-based product. No significant losses occurred in viability of bifidobacteria in fermented camel, cow, and sheep milks during 6wk of refrigerated storage. In conclusion, all 4 varieties of milk proved to be suitable raw materials for the manufacture of ABT-type fermented dairy products that were microbiologically safe and beneficial for human consumption. It was suggested that milk from small ruminants be increasingly used to produce probiotic fermented dairy foods. The development of camel milk-based probiotic cultured milks appears to be even more promising because new markets could thus be conquered. It must be emphasized, however, that further microbiological and sensory studies, technology development activities, and market research are needed before such food products can be successfully commercialized.

Occurrence of anaerobic bacterial, clostridial, and Clostridium perfringens spores in raw goose livers from a poultry processing plant in hungary

Anaerobic bacterial, clostridial, and Clostridium perfringens spores were enumerated in raw goose liver samples taken after evisceration of the birds (EB) in the slaughterhouse and after removal of blood vessels from the liver (RBVL) in the cannery. The samples taken after RBVL had significantly higher (P < 0.05) spore counts than did those taken after EB, indicating contamination of livers during processing. The number of C. perfringens spores was one log cycle higher in the samples taken after RBVL than in those taken after EB (P < 0.05). The confirmation of C. perfringens according to the profiles of Rapid ID 32 A tests was carried out by means of the ATB Plus computer program. With an identification percentage of 99.9 and a T-value of 0.65, the suspect colonies proved to be C. perfringens. Therefore, the importance of an appropriate cleaning and sanitation program and of personnel hygiene should be emphasized in the industry.

Short communication: Viability of culture organisms in honey-enriched acidophilus-bifidus-thermophilus (ABT)-type fermented camel milk

The aim of this research was to monitor the survival during refrigerated storage of Lactobacillus acidophilus LA-5 (A), Bifidobacterium animalis ssp. lactis BB-12 (B), and Streptococcus thermophilus CHCC 742/2130 (T) in cultured dairy foods made from camel and, for comparison, cow milks supplemented with black locust (Robinia pseudoacacia L.) honey and fermented by an acidophilus-bifidus-thermophilus (ABT)-type culture. Two liters of dromedary camel milk and 2 L of cow milk were heated to 90 °C and held for 10 min, then cooled to 40 °C. One half of both types of milk was fortified with black locust honey at the rate of 5.0% (wt/vol), whereas the other half was devoid of honey and served as a control. The camel and cow milks with and without honey were subsequently inoculated with ABT-5 culture and were fermented at 37 °C until a pH value of 4.6 was reached. Thereafter, the probiotic fermented milks were cooled to 15 °C in ice water and were each separated into 18 fractions that were transferred in sterile, tightly capped centrifuge tubes. After 24 h of cooling at 8 °C (d 0), the samples were stored at refrigeration temperature (4 °C). Three tubes of all 4 products (i.e., fermented camel and cow milks with and without honey) were taken at each sampling time (i.e., following 0, 7, 14, 21, 28, and 35 d of storage), and the counts of characteristic microorganisms and those of certain spoilage microbes (yeasts, molds, coliforms, Escherichia coli) were enumerated. The entire experimental program was repeated twice. The results showed that addition of black locust honey at 5% to heat-treated camel and cow milks did not influence the growth and survival of starter streptococci during production and subsequent refrigerated storage of fermented ABT milks. In contrast, honey improved retention of viability of B. animalis ssp. lactis BB-12 in the camel milk-based product during storage at 4 °C up to 5 wk. No spoilage organisms were detected in any of the samples tested in this study. In conclusion, supplementation of cultured dairy foods, especially those made from camel milk, with honey is recommended because honey is a healthy natural sweetener with a variety of beneficial microbiological, nutritional, and sensory properties.